Dear José Antonio,
Could you please clarify in the Authors' documentation the origin of your music? Specifically, it is important to clarify these points:
- The music from WYZ has been specifically created for this game or was a song that existed previously and you are using it with WYZ's consent?
- Have you got explicit consent for using Arkos' demo songs?
These points need to be addressed in the documentation. For authors' explicit consents, it is enough having an email from original authors giving you consent to use their songs in your production. Otherwise, if songs have a license that lets you use them, you can refer to the license.